If a pedestrian were to collide with a motor vehicle, it is preferred that the head of the pedestrian impact on a front hood of the motor vehicle, since the latter can yield under the impact, thereby catching the head relatively carefully. In order for this to succeed, the pedestrian must not be simply thrown over by the vehicle but his legs have to be pushed away under the torso so that the same can fall onto the front hood.
DE 10 2013 002 307 discloses a front part of a motor vehicle, in which a plate-like bumper stiffener extends between the lower region of a bumper covering and an auxiliary frame. When during a collision with a pedestrian the bumper stiffener strikes the lower legs of the pedestrian, it is initially elastically deformed, but subsequently springs back into its rest position in the process pushing the lower legs away from it in travelling direction. Since the torso of the pedestrian is substantially less accelerated at the same time, it topples onto the hood from the top. The bumper stiffener is curved in vehicle longitudinal direction. This prevents sudden non-reproducible collapsing of the bumper stiffener under load but on the other hand also requires a thick wall of the bumper stiffener for reaching a predetermined deformation resistance. In addition, the curved bumper stiffener requires substantial space in vertical direction which cannot be easily satisfied since the bumper stiffener on the one hand has to be accommodated under a cooling module but on the other hand has to be located high enough so as not to strike a curb stone when driving up against such.
Through the possibility of ribbing of the curved bumper stiffener described in DE 10 2013 002 307 a higher stiffness and thus a lower use of material can be achieved. However, pending the ribs yielding locally, a high initial resistance has to be overcome. Since the further deformation behavior depends on the place in which the rib has started to yield, the reproducibility of the deformation is limited.